Why does the 3D Viewport's Start Clip have no effect in Ortho view?
The reason is "when perspective is disabled only the far Clip-End is used":


  A large clipping range will allow you to see both near and far objects, but reduces the depth precision.
  To avoid this...
  
  
  increase the near clipping when working on large scenes.  
  decrease the far clipping when objects are not viewed at a distance.  
  
  
  When perspective is disabled only the far Clip-End is used, very high values can still give artifacts.
  
  This is not specific to blender, all OpenGL/DirectX graphics applications have these same limitations. 




(Source: Blender Manual via Campbell Barton)